1. Field of the Invention
The present invention relates to a sheet processing apparatus and a control method therefor that generates a sheet bundle by placing an insertion sheet on sheets that have been subjected to image formation and discharged from an image forming apparatus, as well as an image forming apparatus, and a program for implementing the control method.
2. Description of the Related Art
Conventionally, there is known an image forming apparatus, such as a copier, where a sheet, such as a color sheet, an OHP sheet, or a pre-printed sheet on which printing has been carried out, placed on a manual feed tray can be inserted at a specified page in a sheet bundle discharged from the image forming apparatus and where a sheet that has been subjected to image formation by a color image forming apparatus can be inserted into a sheet bundle having been subjected to image formation by an image forming apparatus capable of only black and white output. This image forming apparatus has modes such as a front cover mode where a sheet is inserted at a front page of a sheet bundle, a back cover mode where a sheet is inserted at a final page of a sheet bundle, and an interleaving mode where a sheet is inserted at a desired page between the front page and the final page of a sheet bundle, and therefore a sheet can be inserted at a desired page in a sheet bundle.
A sheet inserter that is connected to a sheet discharge side of an image forming apparatus is also known. The inserter has a cassette in which sheets to be inserted are stored, receives recording sheets on which image formation has been performed after discharge from the image forming apparatus, inserts a sheet fed from the cassette between desired recording sheets, and then discharges a sheet bundle in which the sheet has been inserted according to the cover mode, the interleaving mode, or the like from a discharge opening thereof.
A post-processing apparatus that is connected to an image forming apparatus and includes, in addition to a cassette that stores insertion sheets, a finisher that carries out a sheet aligning process and/or a binding process is also known. This post-processing apparatus combines the functions of a finisher and inserter. An image forming apparatus that can clearly inform the user of a difference in orientation of a cover is also known (see Japanese Laid-Open Patent Publication (Kokai) No. 2000-89613).
However, the various conventional apparatuses described above have the following problem. When sheets are inserted as the front cover and the back cover of a sheet bundle, if there is only one sheet insertion tray such as a manual feed tray or an inserter, it will be necessary for the user to change the orientation of the insertion sheets so as to be alternately face up and face down, so that there has been an operability problem in that it is troublesome to set the sheets.
To cope with this, it would be conceivable to provide two inserters, to set sheets in a face-up state as front covers in a one inserter, and to set sheets in a face-down state as back covers in the other inserter. However, since two inserters are provided in this case, the apparatus size is increased and there can be an increase in cost.